Failure of the uterus (or, occasionally, an associated organ or structure) to return to its expected size after the end of a pregnancy; incomplete involution; an instance of this.
Origin
Mid 19th century. From sub- + involution.
Definition of subinvolution in US English:
subinvolution
nounˌsʌbɪnvəˈl(j)uːʃn
Medicine
Failure of the uterus (or, occasionally, an associated organ or structure) to return to its expected size after the end of a pregnancy; incomplete involution; an instance of this.